Mail boxes in the shape of tractors overlook green vegitation near Roca, Neb. Farmers who have spent the past several months staring at parched fields have a new problem: mud. A rainy spring has brought weeks of rains to the middle of the country, and while it hasn't completely ended the historic drought, new forecasts show it sure has helped. (ASSOCIATED PRESS / Nati Harnik)

DES MOINES, Iowa (AP) — As spring rains soaked the central United States and helped conquer the historic drought, a new problem has sprouted: The fields have turned to mud.

The weekly drought monitor report, released Thursday by National Drought Mitigation Center in Lincoln, Neb., showed the heavy rains that also caused some flooding in the last week brought drought relief to the upper Midwest, western Corn Belt and central portions of the Plains.

Farmers may be thankful the land is no longer parched, but it’s too wet to plant in corn country and freezing temperatures and lingering snow have ruined the winter wheat crop.

“Right now, we’re wishing it would dry up so we can get in the field,” said 74-year-old Iowa farmer Jerry Main, who plants corn and soybeans on about 500 acres in the southeast part of the state. He’s measured more than 9 inches of rain since April 18 — and farmers in his area prefer to plant corn by May 10 — at the latest.

Aside from being too wet to plant, it’s been too cold for seed to germinate. Main said temperatures dipped to 27 on Tuesday and to 32 on Wednesday, a chill that’s been widespread across the Midwest.

“We need some heat, it’s been down in the upper 30s at night,” said Darren Walter, 41, who farms near Grand Ridge, Ill. And farmers in southwest Kansas, Oklahoma and Texas have lost a significant portion of their wheat crop because of unusually late freezes, and have begun knocking it down to feed it to livestock.

But just as better crop technology helped U.S. farmers harvest one of their biggest corn crops ever amid the worst drought in decades, it’s likely to save them from a late, wet planting season. There are corn varieties that mature faster, nearly 30 days in some cases, but the shorter the time to maturity, the lower the yield.

Kevin Malchine, who farms 2,100 acres in southeastern Wisconsin, said he did better than expected last year thanks to drought-resistant corn — harvesting 80 percent more than in 1988, the last time there was a comparable drought.

“We took a hit, but it was much better than I would have thought, and that’s just due to the genetics of today,” Malchine, 51, said.

Sandy Ludeman’s 2,500-acre farm in Tracy, Minn., about 50 miles east of the South Dakota border, is covered with snow. A year ago, he had finished planting corn. This year, he’ll be lucky if he can start in two weeks.

“I guess I’m not abnormally concerned about it,” he said. “I’ve farmed close to 40 years, and we’ve had wet springs before, but if it gets too late, it affects our yield.”

Declaring an end to drought requires looking at how much moisture an area has received, how much soaked into the ground and the impact on agriculture, said Richard Heim, a climate scientist at the National Climatic Data Center who helps draft the drought monitor.

“It takes a while for that moisture to percolate down especially if it’s been dry for a long time,” he said. “When the soil is moist enough it can sustain crops, it can sustain other activities you aren’t really in a drought.”

In Illinois, where corn production plunged 34 percent last year, soggy conditions meant only 1 percent of it has been sown this year.

Rob Asbell farms 5,000 acres of corn and soybeans with his dad and uncle in Peoria County in central Illinois. The last week brought more than 6 inches of rain, saturating the fields and putting him woefully behind.

“Everybody’s behind,” the 42-year-old said. “We’re getting to the point now where it’s time to go, tired of sitting around.”

The dry spell hasn’t snapped everywhere, though. It remains solidly in place in parts of California, Colorado, Kansas, New Mexico, Oklahoma, and Texas, according to the drought monitor. It intensified across western Texas, southeastern New Mexico and the Oklahoma panhandle.

It likely won’t keep farmers out of the fields, though. Agriculture giant Monsanto tested a drought-resistant variety of corn last year, and DuPont Pioneer and Syngenta are also marketing similar varieties.

Southwest Kansas farmer Clay Scott said he was one of 250 to test Monsanto’s during last year’s drought and said it yielded more bushels per gallon of water than his fully irrigated corn. He plans to plant about 10 percent of the drought-resistant corn this year, noting that things are again looking extremely dry.

“The countryside’s hurting every time the wind blows,” he said. “It’s really starting to be an issue with blowing dirt,” he said.